Damping device in a structure and damping construction and damping method using those devices

ABSTRACT

A damping device has a liquid vessel into which a liquid is injected having a wave motion water surface such that the wave motion direction of the wave motion of the water surface is in the elongated direction of the vessel. Damping members are provided in order to damp the sloshing of liquid in the liquid vessel, and wave dissipation devices are disposed at a portion not always soaked in liquid in the liquid vessel. Accordingly, the vibration of a construction occurring by wind, earthquake and the like is absorbed by the viscosity resistance occurring between the liquid and the damping members, and the vibration is restricted. Moreover, damping performance can be efficiently exercised by providing various installation arrangements.

BACKGROUND OF THE INVENTION

The present invention relates to a damping device for preventing thehorizontal vibration of a structure from wind and earthquake, the devicedisposed on an upper portion of the structure, and a damping structureand damping method using such a device.

In U.S. Pat. No. 4,226,554, the following proposal is advanced.Horizontal vibration of a structure from an earthquake, wind and thelike is prevented by damping devices, comprising liquid vessels intowhich a liquid having an open water surface is injected, are disposed onthe upper portion of the structure.

However, the above technique does not have an internal constitution of adamping device providing a sufficiently efficient damping, and such atechnique is desired.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a dampingdevice having an internal constitution and an installation form capableof exercising efficient damping performance, and the dampingconstitution and damping method using those devices so as to solve theabove-described defects.

That is, the present invention is comprised of a liquid vessel, intowhich a liquid is injected, having a flattening wave motion watersurface formed in such a manner that the wave motion direction of thewave motion water surface is in the elongated direction of the liquidvessel, damping members such as meshes and partition walls andprojections for damping the sloshing of the liquid in the liquid vessel,and wave dissipation devices provided at a portion not always in theliquid of the liquid vessel.

According to the present invention, the vibration which proceeds fromwind and earthquake in a structure such as a multistory building andtower can be efficiently absorbed by sloshing the liquid in each dampingdevice. And, since there are no mechanical moving parts in the liquidvessel, the device will be reliable over time in comparison with amechanical damping arrangement. And, it can be easy to performinspection and maintenance. If a high wave occurs in the liquid of avessel, sloshing with a large amplitude, the energy is efficientlyabsorbed by means of wave dissipation devices. Therefore, the cycle ofthe liquid will not be disturbed and the device is sufficientlyreliable.

The damping device is comprised of a liquid vessel, into which theliquid is injected, having the flattening wave motion water surfaceformed in such a manner that the wave motion direction of the wavemotion water surface is in the direction of elongation of the liquidvessel, and damping members such as meshes and partition walls andprojections for damping the sloshing of the liquid in the liquid vessel.With the above-described constitution, plural damping devices aredisposed in such a manner that the elongated direction of the liquidvessel of each damping device faces in different horizontal directionsof the structure.

According to this constitution, the vibration in the horizontaldirection from wind and earthquake in a structure such as a multistorybuilding or tower can be efficiently absorbed by relating each suchvibrational direction to the sloshing direction of the liquid in eachdamping device.

Furthermore, the damping device is comprised of a liquid vessel intowhich a liquid is injected having a flattening wave motion watersurface, is formed in such a manner that the wave motion direction ofthe wave motion water surface is in the elongated direction of thevessel, and has damping members such as meshes and partition walls andprojections for damping the sloshing of the liquid in the liquid vessel.With the above-described constitution, the damping devices are thendisposed on the upper portion of a structure such that the dampingdevices at a side of the structure distant from the center of rigidityof the structure, such as a side face, are greater in number than thoseon the reverse side of the structure, closer to the center of rigidity.

According to this constitution, in case the center of rigidity of astructure is shifted from the center of gravity in the horizontal plane,the vibration energy can be absorbed as equally as possible. Torsionalvibration, with the center of rigidity as its center, can also beefficiently absorbed.

Moreover, in an existing structure being provided an elevated water tankon its upper portion, such as a multistory building and tower, theconstitution is such that resistance members, such as meshes andpartition walls and projections, are provided in the elevated water tankand wave dissipation devices are provided at the upper portion of theelevated water tank. Then, the vibration in an existing structure isrestricted by the resistance between the resistance member and the waterstored in the elevated water tank.

According to this constitution, the damping function toward thevibration by wind and earthquake can be added only by providingresistance members in an elevated water tank which is provided at anexisting structure such as a multistory building and tower. And, sinceinstallation of complicated machinery is unnecessary, the installationis easy. Moreover, a specific installation space is unnecessary, becauseutilization of an existent elevated water tank and the installation onan existing structure can be easy.

Moreover, plural damping devices may be disposed so as to be spacedvertically along a structural body. According to this construction, thevibration of a structure having a high-level natural vibration with acomplicated vibration mode can be efficiently damped. The arrangement issuch that the damping devices are disposed at the maximum amplitudeportion of the primary natural vibration, and at least at the secondarynatural vibration portion, of a structural body. Damping is then carriedout at the maximum amplitude portions toward vibrations having mixedvibration modes. The damping effect is thus efficiently provided.

Furthermore, the arrangement may be such that plural damping devices arevertically spaced along a structural body, with varying sizes of theliquid vessels. Thus each position being provided a liquid vessel has nowasted space. Therefore, the limited space of a structure can beefficiently utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view showing an example of a structure to whichthe present invention is applied;

FIG. 2 is a perspective view showing an example of the arrangement ofdamping devices according to the present invention;

FIG. 3 is a top view showing an embodiment of a damping device of thepresent invention;

FIG. 4 is a front sectional view of the damping device of FIG. 3;

FIG. 5 is a top view showing another embodiment of the damping device ofthe present invention;

FIG. 6 is a front sectional view of the damping device of FIG. 5;

FIG. 7 is a top view showing another embodiment of a damping device;

FIG. 8 is a front sectional view of the damping device of FIG. 7;

FIG. 9 is a perspective view showing another arrangement of dampingdevices according to the present invention;

FIG. 10 is a top view of FIG. 9;

FIG. 11 is a top view showing another arrangement of damping devicesaccording to the present invention;

FIG. 12 is a top view showing a further arrangement of damping devicesaccording to the present invention;

FIG. 13 is a front elevational view showing another structure usingdamping devices;

FIG. 14 is a top view of another arrangement of damping devicesaccording to the present invention;

FIG. 15 is a top view of another arrangement of damping devices;

FIG. 16 is a front sectional view of another damping device;

FIG. 17 is a top view showing the arrangement and construction ofdamping devices according to the present invention;

FIG. 18 is a top view showing another arrangement and construction ofthe damping devices of the present invention;

FIG. 19 is a front sectional view showing another example of a dampingdevice according to the present invention;

FIGS. 20 through 22 are illustrations of vibration modes of a structure;

FIG. 23 is a front elevational view showing an embodiment of a dampingstructure; and

FIG. 24 is a front elevational view showing another embodiment of adamping structure.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A multistory building 1 has a structural body 3, which is built on theground 2 as shown in FIG. 1, and plural damping devices 5 are disposedon an apical portion 3a of the structural body 3. Two damping devices 5are disposed so as to extend perpendicularly to each other, as shown inFIG. 2. Each damping device 5 has a liquid vessel 5a on which a lidmember 5g is provided on an upper portion thereof, and the form of thevessel 5a is rectangular, as shown in FIGS. 3 and 4. The liquid 5b,which is water, or a liquid having the same viscosity as water or ahigher viscosity than water, is injected into each liquid vessel 5a.Wave motion water surface 5f, wave motion occurring by sloshing theliquid 5b, is formed in the shape of a rectangle in the liquid vessel 5aby injected liquid 5b, as shown in FIG. 2. Two mesh portions 5c actingas damping members and comprising stainless steel, vinylon, highefficiency fiber and the like are provided at two levels, thus formingupper and lower portions, as shown in FIG. 4. Damping members are thusat both sides, right and left in the liquid vessel 5a in FIG. 3. Mesh 5cis also provided perpendicularly at the center portion of FIG. 4. Wavedissipation devices 5h, 5h are provided at both sides of the lid member5g at the upper portion of the liquid vessel 5a. Each wave dissipationdevice 5h is composed of a porous member formed by a block of scrapiron, crushed stone, metal chip and the like, or an aggregation ofmeshes provided by superimposing a number of meshes 5k in the horizontaldirection, as shown in FIG. 19.

With the above-described constitution of a multistory building 1, whenthe structural body 3 vibrates from an earthquake, gusts of wind and thelike, the damping device 5 provided at the apical portion 3a alsovibrates. Then the liquid 5b in the damping device 5 sloshes in theelongated directions WD of the wave motion water surface 5f,synchronizing with the vibration of the structural body 3, as shown inFIGS. 3 and 4. That is, the liquid 5b easily starts sloshing accordingto the vibration of a multistory building 1 by harmonizing the sloshingcycle of the liquid 5b with the primary natural vibration cycle of themultistory building 1, and the vibration energy of the multistorybuilding 1 is absorbed by its wave motion. The sloshing cycle of theliquid 5b is determined by the length L1 in the long side direction ofthe liquid vessel 5a and the height of liquid L3 of liquid 5b in astationary condition, as shown in FIGS. 3 and 4. When the liquid 5bsloshes, the liquid 5b passes the meshes 5c provided in the liquidvessel 5a in the up and down directions in FIG. 4, as shown by thearrows AR. At this time, a viscosity resistance acting between theliquid 5b and the meshes 5c acts in the direction in which the movementof the liquid 5b is restrained. That is, the meshes 5c acting as dampingmembers reduce the amplitude of the waves of of the liquid in thevessel, while still allowing the reduced amplitude wave to continue itswave motion. Accordingly, the sloshing of the liquid 5b is damped, andthe ability of the structure to absorb the power of the vibration energyis improved.

When the vibration of the structural body 3 becomes greater than apredetermined value, the height of the wave of the liquid 5b in thedamping device 5 also becomes higher. Then, an apical portion 5j of awave 5i reaches the lid member 5g as shown in FIG. 4. However, when theapical portion 5j of the wave directly collides with the lid member 5gand rebounds, the cycle of the liquid 5b is disturbed, and it becomesimpossible to exercise the proper damping effect. But the wavedissipation devices 5h, 5h are disposed at both sides of the device inthe direction of the wave motion where the apical portion 5j of the wave5i is produced in the liquid vessel 5a. The wave 5i will flow into themany cavities of the porous member of a wave dissipation device 5h, thewave 5i colliding with the wave dissipation device 5h, and its energywill be efficiently absorbed. Therefore, the wave does not rebound andconfuse the motion cycle in the vessel. Furthermore, the wavedissipation device 5h prevents waves from colliding with the lid member5g directly. Therefore, excess pressure does not occur on the lid member5g by the wave, and the disturbance of the motion cycle by the lidmember 5g can be prevented. That is, the wave dissipation devices 5habsorb and dissipate waves above a predetermined amplitude such thatwave amplitude above the predetermined amplitude is absorbed anddissipated and prevented from reflecting and interfering with the wavemotion cycle in the elongated vessel. Accordingly, the vibrationabsorbing operation of the damping device 5 is smoothly performed.

The above embodiment has described the meshes 5c as used as dampingmembers provided in the liquid vessel 5a. But, any configuration, form,and installation mode of a damping member is available, as long as thedamping member can damp the sloshing of the liquid 5b in the liquidvessel 5a. For example, it may be that plural meshes 5c are provided insuch a manner that the liquid vessel 5a is divided in the verticaldirection of FIG. 6, as shown in FIGS. 5 and 6. Furthermore, it ispossible that the meshes 5c are contiguous in the vertical direction andthe horizontal direction of the liquid vessel 5a, as shown in FIGS. 16and 19. If the meshes 5c are provided at both sides of the liquid vessel5a at levels, the height of the wave 5a of the liquid 5b can berestricted by the meshes 5c provided at those levels. Therefore thedamping efficiency can be exercised toward earthquakes and the likeoccurring with larger vibrations.

And, besides members 5c, partition walls 5d may be provided partitioningthe liquid vessel 5a in the direction of the wave motion of the liquid5b in the liquid vessel 5a, that is, in the right and the left directionin the figure as shown in FIGS. 7 and 8. The water surface of the wavemotion 5f is thus divided into plural portions. Moreover, manyprojections 5e are disposed at the partition walls 5d, for example inthe shape of dents on the center portion, as shown in FIG. 8. Then thevibration of the liquid 5b is damped by the viscosity resistanceoccurring between the projections 5e and the liquid 5b. Theabove-described method is naturally available. Moreover, a chip ofsteel, plastic moulding goods and the like can be disposed in the liquidvessel 5a as a damping member.

The arrangement forms of the damping devices 5 can be properly selectedaccording to the arrangement place and the necessary damping effect.Since the wave motion of the liquid 5b occurs in the elongated directionof each damping device 5, the damping devices 5 are disposed in such amanner that the elongated directions WD of the water surface of the wavemotion 5f of each damping device 5 face in at least two directions ofthe structure 1 to absorb the vibrations. Then, the vibration acts onthe damping devices 5 in two directions at least, and a high dampingeffect can be achieved. For example, as shown in FIGS. 9 and 10, pluraldamping devices 5 can be arranged so that the elongated directions WD inwhich the water surface of the wave motion 5f forms the wave motion facetwo horizontal directions orthogonal to each other. Accordingly, thevibration in the two orthogonal directions occurring at the structure 1can be effectively absorbed. Moreover, in the arrangement and form ofthe damping devices 5, many damping devices 5 can be arranged along theexternal wall 1a of the structure 1 as shown in FIGS. 11 and 15. (In thecase of FIG. 15, the damping devices are also disposed at the center ofthe structure 1.) In such a case, if there is existing equipment, suchas a machine room of an elevator, at the apical portion 3a of thestructure 1, the damping devices 5 can be disposed to avoid suchexisting equipment, and the construction space can be effectivelyutilized. If the building has a circular structure 1, many dampingdevices may be disposed along the external wall 1a of the circle, asshown in FIG. 12. And of course the damping devices 5 can be disposedradially, as shown in FIG. 14. Furthermore, the damping effect can besubstantially improved by arranging the damping devices along theexternal wall 1a of a structure 1, at which point the vibrationamplitude becomes bigger.

In case the position of the center of gravity W of the structural body 3shifts from the position of the center rigidity G (in FIG. 17, theposition of the center of gravity W locates the center in the up anddown directions and in the right and left directions in the structuralbody 3 in the figure, and the position of the center of rigidity Glocates the center in the up and down directions and is to the right tosome extent in the figure in comparison with the center gravity W), thestructural body 3 generates torisional vibration, with the center ofrigidity G as its center, in the directions as shown by the arrows A andB. Then, the farther the distance from the center of the rigidity G is,the bigger the amplitude of the torsional vibration of the structuralbody 3 becomes. In FIG. 17, the amplitude of the side face 3b on theleft in the figure becomes bigger than that of the side face 3c on theright. Then, since the vibration energy of the side face 3b becomesbigger than that of the side face 3c, it is necessary that the vibrationabsorbing ability of the side face 3b side is bigger than that of theside face 3c side in order to absorb the vibration properly. When thenumber of damping devices 5 disposed at the side face 3b, having adistance L4 from the center of rigidity G, is more than that disposed atthe side face 3c, having a distance L3 from the center of rigidity G,the absorbing quantity of the vibration energy of the side face 3b sideincreases. In result, the vibration in the directions shown by thearrows A and B of the structural body 3 is smoothly and thoroughlyabsorbed relative to both sides, the right and left of the center ofrigidity G.

In case the position of the center of rigidity G is shifted in the upand down directions of the structural body 3 as well as in the right andleft directions as shown in FIG. 18 (In FIG. 18, the position of thecenter of gravity W locates the center in the up and down directions andin the right and left directions of the structural body 3 in the figure.The position of the center of rigidity G is in the upper portion in thefigure to some extent and to the right of the center of gravity W.), theamplitude of the side face 3b, having the distance L4 from the center ofrigidity G, and the amplitude of the side face 3e, having the distanceL6 from the center of rigidity G, become big. Accordingly, the number ofthe damping devices 5 to be disposed on the side faces 3b and 3e isgreater than that on the side faces 3c and 3d at distances L3 and L5from the center of rigidity G, respectively. Therefore, the vibrationabsorbing ability of the side faces 3b and 3e is increased, and thevibration of the structural body 3 is smoothly absorbed withoutunbalance.

A structure having comparatively long vibration cycles in the flexiblestructure is suitable for structures to which the damping devices 5according to the present invention are applied. Of course a tower 6,comprising a steel frame and the like as shown in FIG. 13, can bedamped, as well as the multistory building 1 shown in FIG. 1.

The damping effect is exercised in such a manner that, concerning thequantity of the liquid 5b in the liquid vessel 5a, the weight of freewater is 0.5-2% of the weight of a structure (the greater the weight offree water, the higher the damping effect), and the damping constant bymeans of the damping member is about 2-10%.

The above embodiment described the wave dissipation devices 5h asdisposed at both sides of the vessel in the wave motion directions WD ofthe liquid vessel 5a. However, the wave dissipation devices 5h do notalways have to be disposed at both sides of the liquid vessel 5a. Anyplace is available as an installation location of the wave dissipationdevices, as long as they are not always soaked in the liquid 5b. Ofcourse the devices can be disposed at all faces of the upper portion orall faces of the sidewall of the liquid vessel 5a.

Furthermore, the form of the structure 1 is not always a square form asshown in FIGS. 17 and 18. Any form, for instance a polygonal or curvedform, can be used.

The damping devices according to the present invention can be used bothwith a new structure and an existing structure. For instance, thedamping devices can be retrofitted at the upper portion of an existingstructure.

With respect to modes of vibration occurring on the structural body 3,there are higher-level modes such as secondary and tertiary modes aswell as a primary vibration mode. These vibration forms are as follows:in the primary mode, a maximum amplitude portion M1 exists at the upperedge of the structural body 3, as shown in FIG. 20 (In FIGS. 20 through22, the structural body 3 is indicated by a line in order to easilyunderstand the explanation). However, the secondary vibration mode issubstantially different from the primary mode, as shown in FIG. 21, andmaximum amplitude portions M2 and M3 occur not only at the upper edge ofthe structural body 3 but also at a lower portion, to some extent, incomparison with a center portion. Moreover, in the tertiary vibrationmode, as shown in FIG. 22, maximum amplitude portions M4, M5 and M6occur at the upper edge of the structural body 3, an upper portion incomparison with the center, and a lower portion in comparison with thecenter, respectively.

Accordingly, to install the damping devices 5 only on the upper portionof the structural body 3 is useful to counteract the primary vibrationmode, but may lack effectiveness for the secondary vibration mode orhigher level vibration modes.

Therefore, as shown in FIG. 23, the damping devices 5_(A) in which theliquid 5b is stored are disposed at the upper portion of the structuralbody 3, that is, at the maximum amplitude portion M1 in the primarynatural vibration of the structural body 3. In this case, the liquid 5bhas a sloshing cycle corresponding to the primary natural frequency ofthe structural body 3 (ordinarily the cycle corresponds with the primarynatural frequency). Moreover, damping devices 5_(B) in which the liquid5b is stored are disposed at the maximum amplitude portions M2 and M3 inthe secondary natural vibration of the structural body 3. In this case,the liquid 5b has the sloshing cycle corresponding to the secondarynatural frequency of the structural body 3 (ordinarily it correspondswith the secondary natural frequency). The shorter the sloshing cycle ofthe storing liquid 5b, that is, the higher the frequency, the smallerthe liquid vessel 5a comprising the damping devices 5.

By taking the above-described measures, in the structural body 3 isshown in FIG. 23, the primary vibration is efficiently absorbed by meansof the damping devices 5_(A) and the secondary vibration is efficientlyabsorbed by means of the damping devices 5_(B) in case of earthquake andthe like. Furthermore, in order to improve damping efficiency, dampingdevices 5_(C) in which the liquid 5b is stored are disposed at themaximum amplitude M4, M5 and M6 in the tertiary natural vibration asshown in FIG. 24 as well as damping actions toward the primary and thesecondary vibration by means of the damping devices 5_(A) and 5_(B) asshown in FIG. 23. In this case, the liquid 5b of the damping devices 5chas a sloshing cycle corresponding to the tertiary natural frequency ofthe structural body 3 (ordinarily, it corresponds with the tertiarynatural frequency). Then, the damping efficiency of the structural body3 is expanded to the tertiary natural vibration portion.

Heretofore, the present invention has been explained on the basis of theabove-described embodiments. But, the embodiments which are mentioned inthe present specification are merely exemplary. The scope of theinvention is designated by the accompanying claims, and is not to berestricted by the descriptions of the preferred embodiments.

We claim:
 1. A damping device for absorbing vibrations of a structure byproviding said damping device on an upper portion of the structure, saiddamping device comprising:an elongated vessel for containing a liquidtherein such that movement of the vessel will create a wave motion ofthe liquid surface in the elongated direction of the vessel; a pluralityof damping means disposed inside said vessel for reducing the amplitudeof a wave of the liquid in said vessel while substantially allowing thereduced amplitude wave to continue its wave motion; and wave dissipationmeans for absorbing and dissipating waves above a predeterminedamplitude such that wave amplitude above said predetermined amplitude isabsorbed and dissipated and prevented from reflecting and interferingwith the wave motion cycle in said elongated vessel.
 2. The dampingdevice as set forth in claim 1, wherein:said wave dissipation meanscomprises at least one porous member fixed in an upper portion of saidvessel above a mean surface level of the liquid.
 3. The damping deviceas set forth in claim 2, wherein:said wave dissipation means comprisestwo said porous members, one said porous member fixed at each end ofsaid vessel in the elongated direction.
 4. The damping device as setforth in claim 2, wherein:said porous member comprises a plurality ofsuperimposed horizontal meshes.
 5. The damping device as set forth inclaim 1, wherein:said plurality of damping members are distributed insaid vessel so as to have at least one damping member disposed on eachside of a midpoint of said vessel in the elongated direction.
 6. Thedamping device as set forth in claim 1, wherein:said plurality ofdamping members comprises a plurality of meshes disposed in said vessel.7. The damping device as set forth in claim 6, wherein:at least one ofsaid meshes is vertically disposed in said vessel.
 8. The damping deviceas set forth in claim 6, wherein:said meshes are horizontally disposedin said vessel.
 9. The damping device as set forth in claim 6,wherein:said plurality of meshes comprises at least one vertical meshdisposed in a central portion of said vessel and horizontal meshesdisposed at end portions of said vessel.
 10. The damping device as setforth in claim 3, wherein:said plurality of damping members comprises atleast one vertical wall extending in the elongated direction of saidvessel, said vertical wall having a plurality of projections for dampingthe sloshing of the liquid.
 11. The damping device as set forth in claim10, wherein:said at least one vertical wall comprises a plurality ofvertical walls inside said vessel extending in the longitudinaldirection of said vessel to thereby partition said vessel into aplurality of elongated chambers, each said vertical wall having aplurality of projections for damping the sloshing of the liquid.
 12. Thedamping device as set forth in claim 1, wherein:said plurality ofdamping members includes damping members disposed in a lower portion ofsaid vessel such that said damping members will always be in at leastpartial contact with liquid sloshing in said vessel.